In coiled tubing operations, pressurized fluid is delivered from pumping equipment to the inside of the coiled tubing byway of a rotating swivel. Current swivels have several drawbacks. Today's rotating swivels use standard market hydraulic seals meant to contain axial pressure in a static condition. However, operational pressures are not typically static in nature and involve complex combinations of pressure variances, which degrade the service life of such hydraulic seals. Further, serviceability of current swivels, particularly replacing seals within the swivel, is inherently difficult and time consuming. Generally, the swivel must be completely removed from the tubing reel, repaired at a servicing facility, and reinstalled as a complete unit, which can take an entire coiled tubing unit out of service for a lengthy period of time. Finally, friction caused by fluid flow through current swivels erodes the interior of the swivel and deteriorates the high pressure seals in direct contact with fluids in the interior chamber of the swivel. Therefore, there is a need for an improved swivel assembly that addresses deficiencies of current swivels.
In one aspect, embodiments disclosed herein relate to an oilfield assembly comprising a pump in fluid communication with a string of coiled tubing on a tubing reel through a coiled tubing swivel assembly, the coiled tubing swivel assembly comprising a fluid inlet segment coupled to a swivel body having a central axis, and a rotatable hollow shaft having a portion that extends axially within the swivel body, wherein the fluid inlet segment, swivel body and rotatable hollow shaft form a conduit for passage of a pumped substance to the tubing reel from the pump, the rotatable shaft comprising a first end attachable to the tubing reel, and a distal second end, at least pan of which is configured to engage a corresponding indentation in the body.
In other aspects, embodiments disclosed herein relate to an oilfield assembly comprising a pump in fluid communication with a string of coiled tubing on a tubing reel through a coiled tubing swivel assembly, the coiled tubing swivel assembly comprising a fluid inlet segment coupled to a swivel body having a central axis, the swivel body comprising a removable end cap coupled to a swivel housing, a rotatable shaft insertable within the swivel housing, wherein the fluid inlet segment, swivel body and rotatable shaft form a conduit for passage of a pumped substance to the tubing reel from the pump, the rotatable shaft comprising a first end attachable to the tubing reel, and a second end configured to abut the end cap, wherein the rotatable shaft and the end cap comprise coaxial inner bores, and wherein a distance from the central axis to the end cap inner bore is equal to or less than a distance from the central axis to the shaft inner bore; and one or more rotary seals arranged circumferentially around an outer surface of the shaft and proximate to the distal second end of the shaft.
In yet other aspects, embodiments disclosed herein relate to a method using an oilfield assembly comprising a pump in fluid communication with a string of coiled tubing on a tubing reel through a coiled tubing swivel assembly, the coiled tubing swivel assembly comprising a fluid inlet segment coupled to a swivel body having a central axis, a rotatable hollow shaft having a portion that extends axially within the swivel body, wherein the fluid inlet segment, swivel body and rotatable hollow shaft form a conduit for passage of a pumped substance to the tubing reel from the pump, the rotatable shaft comprising a first end attachable to the tubing reel, and a distal second end, at least part of which is configured to engage a corresponding indentation in the body, thereby preventing direct contact between the distal second end of the shaft and the pumped substance, one or more rotary seals arranged circumferentially around an outer surface of the shaft and proximate to the distal second end of the shaft, one or more bearing assemblies disposed radially between the rotatable shaft and the swivel body; circumferentially arranged set screws configured to engage an innermost bearing assembly and a bearing retainer configured to engage an outermost bearing assembly. A method of disassembling the coiled tubing swivel assembly includes the steps of loosening the set screws from against the innermost bearing assembly, uncoupling the end cap from the swivel housing and removing the end cap; and inspecting or replacing the one or more rotary seals disposed at the second end of the shaft.